Process of separating fibrous pulp into springwood and summerwood fibers by centrifuging



Nov. 14, 1967 v G. E. MALM 3,352,745

PROCESS OF SEPARATING FIBROUS PULP INTO SPRINGWOOD AND SUMMERWQOD FIBERSBY CENTRIFUGING Filed Feb. 27, 1961 PULP I OI/GIMQL Wm WLPI O/P/G/WLPULP INVENTOR ATTORNEYS United States Patent M 3,352,745 PRQQESS 0FSEPARATHNG FIERGUS PULP INTO SPRINGWOQD AND SUMMERWOOD FIBERS BYCENTREFUtEING Gustaf E. Mains, Sundsvall, Sweden, assignor to SvenskaCellulosa Alrtiebolnget, Sundsvall, Sweden Filed Feb. 27, 1961, er. No.91,890 Claims priority, application Sweden, Feb. 29, 1960, 2,033/60 1Claim. (Cl. 162-55) The present invention relates to a method oftreating fibrous pulp suspensions, containing fibers of different kinds,preferentially suspensions of cellulose pulp containing springwoodfibers and summerwood fibers (unbleached, semibleached or all-bleached),in such a manner as will cause the fibers contained in the suspensionsto become separated from each other in conformity with p the inherentcharacters of the fibers. In the present connection fibers of differentkinds means such fibers as differ from each other in respect of theirmorphologic structure and/or specific gravity, specific surface as wellas chemical and/or physical properties and which, because of this, whenfurther refined to paper products and/or to packing products and,respectively, to textile fibers, to chemical products etcetera yielddifferent results in respect of the quality and properties of the finalproduct. Examples hereof are the abovementioned springwood fibers andsummerwood fibers. The purpose of the separation is to produce, asdesired, merely from the obtained fiber fractions or from fractionsmixed with each other and/ or mixed with other fractions or pulps, pulpshaving, for example, different paper-technical properties and,respectively, different derivative-technical properties.

According to the invention the fibrous pulp suspension to be treated issubjected to the action of centrifugal force or centrifugal force incombination with a pumping force and/ or the force of gravity within atleast one chamber of treatment connected to a source of suction and/or asource of pressure, for example, a centrifugal or vortex separator, aso-called centricleaner, the various fractions resulting from theseparation treatment being then led away from said chamber of treatmentin order to constitute, or to be added to, the pulp in which eachrespective fraction is to be included, after the fibers of suchfractions having, if desired, first been, wholly or partly, subjected tofurther separation and/or mixing with other fractions or pulps. Theseparation of the fibers-which preferably are suspended in water butwhich, of course, may be suspended in any other suitable liquid orgaseous medium-can be carried out in one or more steps and underconditions which in each separate case are adapted to the variousqualities of pulp to be produced. The chambers of treatment may then beconnected in parallel and/or in seriesdirectly and/or in accordance withthe principle of so-called cascade connection. The concentration of thefibrous pulp amounts to 0.005-2 percent, preferably to 0.011.6 percent,and preferentially to 0.05-1.3 percent, and the temperature amounts to0-70 C., preferably to 0-60 C., and preferentially to 1-50 C. Thepumping pressure at the inlet end of the chamber of treatment amounts to02-15 kgs./sq. cm., preferably to 03-12 kgs./sq. cm., and preferentiallyto 1-8 kgs./sq.,

cm. The counter-pressure, is 0.0- kgs./ sq. cm., prefer- 3,352,745Patented Nov. 14, 1957 ably 0.0-5 kgs./sq. cm., and preferentially 0.0-2kgs./sq. cm. The pH-value of the pulp suspension amounts to 1-13,preferably to 2-12, and preferentially to 3-10.

The quantitative proportions of the pulps obtained by the separationtheso-called separated pulpsare adapted to, inter alia, the quantitativeproportions and the properties of the components contained in the pulpto be treated-the so-called original pulpand., respectively, to theproperties that the separated pulp should have.

Thus, the invention makes it possible to separate fibers havingdifferent structures and/or properties and compositions, respectively,such as the abovementioned springwood fibers and summerwood fibers.Since, as is well known, fibers of different types-inter alia springwoodfibers and summerwood fibers-yield papers of different types it is,thus, possible in accordance with the invention, to produce, as desired,from an original pulp of a normal or of a special type, containingdifferent fiber components, two or more pulps having differentproperties.

What has been said above also applies to pulps for other purposes, forexample, for textile fibers and for fibers intended for chemicalproducts or for packing materials, for example, so-called liners andcardboard.

In the accompanying drawings FIG. 1 is a schematic illustration of a onestep separation in a vertix separator of so-called centricleaner, and

FIG. 2 is a schematic illustration of a two step separation.

Referring to the drawings 1 is a typical known conical vortex separatoror so-called centricleaner having a tangential inlet 2 for the pulp tobe treated, an outlet 3 for the lighter fraction designated pulp 1 andan outlet 4 for the heavier fraction designated pulp II. As appears inFIG. 2 the lighter fraction leaving the centricleaner 1 through theoutlet 3, Le. pulp I is delivered into a second centricleaner 1a inwhich it is again divided into lighter and heavier fractions designatedpulps III and V which leave the centricleaner 1a through the outlets 5and 6 respectively. At the same time the heavier fraction leaving thecentricleaner 1 through the outlet 4 i.e. pulp II, is delivered to athird centricleaner 1b in which this fraction is separated into lighterand heavier fractions designated pulps IV and VI which leave thecentricleaner 1b through the outlets 7 and 8 respectively.

Some examples, elucidating the application of the invention inconnection with the separation of fibers in various kinds of cellulosepulps, are given below.

Example 1.-Separation, in one step, of fibers in unbleached pinesulphate pulp The separation was carried out in one step in a number ofvortex separators, so-called centricleaners, at a pulp concentration ofabout 0.25 percent. The pump pressure of the entering pulp suspensionwas 3 kgs./sq. cm. with a counterpressure of the leaving pulp suspensionamounting to about 0.1 kg./sq. cm. The pH-value of the pulp suspensionamounted to 6.5. The temperature was +20 C. The diagram of connectionsof such a vortex separator will appear from the accompanying FIGURE 1 ofthe drawing, the analytical data of the pulps being whereas the fractionindicated as pulp II yielded a paper having a low breaking length and ahigh tear factorthe paper was very porous and bulky.

Example 2.--Separatin, in one step of fibers in bleached pinesulphatepnlp The separation was carried out in the same way as inExample 1. The analytical dataof the pulps will appear from Table 2(below). Said table shows that by the separation the original pulp hasbeen divided into two fractions possessing entirely differentproperties. For purifying the fraction indicated by II, which is, infact, or which may be, not so pure as the pulp indicated by I, asuitable way of proceeding is as follows:

(1) Screening the pulp in a known manner.

(2) Treating the pulp in vortex separators in at least one, preferablyin two or more steps, the return connections being used in the mannerwhich is the most suitable one for the pulp or the pulps desired.

Example 3 .S eparation, in two steps, of fibers in unbleached pinesulphate pulp The separation was carried out in two steps in accordancewith the diagram of connections appearing from the accompanying FIGURE 2of the drawing. The concentration of the pulp at the test amounted to0.3 percent and the temperature amounted to +16 C. The pump pressure ofthe entering pulp suspension was 3 kgs./sq. cm. and the counterpressureof the leaving pulp suspension amounted to about 0.1 kg./sq.-cm.- ThepH-value of the suspension was 6.9. The analytical data of the pulps arefound in Table 3 (below), which shows that the connections used'in thiscase resulted in pulps of entirely different characters. The pulps I,III and V are exceptions, said pulps being rather of the same character.Consequently, in the present case it is possible to restrict oneself tofirst separating the original pulp into pulps I and II, pulp II beingthen separated into pulps'IV and VI. Said pulps, IV and VI, may then intheir turn be separated in a suitable manner, according to thedesiderata existing in respect of the number of qualities and,respectively, the properties of the qualities. Pulp IV and fractionsthereof in the. accepted fractions as Well as in the rejected fractionspreferably may be screened and/or treated in a vortex separator.

Example 4 .-Separation, in one step, of fibers in unbleached birchsulphate pulp The original pulp was treated under, the same conditionsas in Example 1. The analytical data of the pulps will appear from Table4 (below), which shows that the pulps obtained by the separation-arerather similar to each other and also similar to the original pulpexcept in respect of the porosity and the volume-weight of the papermade thereof.

Example 5 .---Separation, in one step, of fibers in unbleached sprucesnlp/zile pulp The separation was carried out under conditions similarto those in Example 1. The analytical data of the pulps are to be foundin Table 5 (below), from which it will appear that the original pulp hasbeen separated into two pulps having different paper-technicalproperties.

As previously mentioned the vortex separators, the socalledcentricleaners, used for the separation, may be connected in paralleland/or in series-directly and/or according to the principle of so-calledcascade connection.

TABLE 1.DATA OF ANALYSIS OF THE ORIGINAL PULP AND OF THE SEPARATEDPULIS, RESIECTIVELY (UNBLEACIIED PINE SULPHATE PULP) Valley beating ofdried pulp Fiber Pulp Chlorine meter Degree Time Breaking Burst TearFolding Porosity; Absorp- Volume number weight, of beating of beating,length, factor factor number see/100 tion, weight,

mgJm. SR min. km. cu. cm. mm. gJcu. cm.

13 0 2.4 16 0 70 0.37 Original pulp 1 5. 5 0. 194 25 10. 4 81 129 4, 00025 33 0. 45 11.8 91 111 4, 400 390 12 0.70 14 0 39 27 3 44 0. 48 Pulp I1 -5. 6 0. 160 25 52 10.8 99 4,000 85 21 0.71 45 74 12. 2 96 81 4, 500900 6 0. 77 13 0 1.3 8 0 80 0.33 Pulp II -5. 2 0. 233 25 50 9.0 70 1493, 500 19 48 0. 00 45 72 10. 6 85 125 4, 300 150 17 0. 67

1 The pulps screened before being analyzed, screening resi(lne=0.l7

TABLE 2.DATA OF ANALYSIS OF THE ORIGINAL PULP AND OF THE SEPARATEDPULPS, RESPECTIVELY (BLEACI'IED PINE SULIHATE PULP) Valley beating ofdried pulp Whiteness, Fiber Pulp percent meter G.E. weight, Degree ofTime of realring Burst Tear Folding Porosity, Absorp- Volume mg./n1.beating, beating, length, factor factor number see/ tion, weight,

S min. km. cu. em. mm. g./eu. cm.

Original pulp 14, 5 0 2. 0 16 1 104 0. 4? 86.0 0. 190 25 35 8.4 66 1052,900 37 34 0.70 45 57 9. 4 72 90 3,100 640 17 0. 74 15. 5 0 2. 2 l6 10. 48 Pulp I 86,1 0.157 25 32 8.5 70 103 2, 700 47 33 0. GS 45 53 9. 578 88 3, 400 840 17 0. 74 12. 5 0 1. 4 10 -1 0 110 0. 43 Pulp II 85.60.235 25 38 7.8 66 114 2,300 22 41 0. 65 45 56 8. 6 72 99 2, 800 340 200. 71

The expression fiber meter weight" means the weight in milligrams of 1meter length of fibers placed and to emit TABLE 3.DATA OF ANALYSIS OFTHE ORIGINAL PULP AND OF THE SEPARATED PULPS, RESPECTIVELY (UNBLEACH- EDPINE SULPI-IATE PULP) Valley beating Pulp Degree of Time of BreakingBurst Tear Folding Prosity, Absorp- Volume beating, beating, length,factor factor number sec./l n11. tion, mm. weight,

SR min. km g./cm. cu.

Original pulp 13. 0 3. 4 22 0 75 0.42 25 47 10. 5 81 113 3, 700 36 29 0.67 45 72 12.0 96 100 4, 400 800 9 O. 72 13 0 3. 2 20 0 81 0. 39 25 4910. 4 82 118 4,000 26 4O 0. 67 45 74 11. 8 93 101 4, 600 700 11 0. 73Pulp I 13. 5 0 3. 8 26 1 65 0. 44 25 44 10. 6 81 110 2, 900 38 30 0.6845 68 12. 2 97 94 4, 500 900 8 0. 73 Pulps separated from pulp 1:

Pulp III 14 0 4. 0 28 1 57 0. 45 25 46 10. 9 84 164 3, 000 65 25 0. 7045 67 12. 4 9S 2 4, 500 920 7 O. 74 Pulp V 14 0 2. 5 15 0 67 0 42 25 489. 9 79 122 8, 800 19 40 0. 65 45 74 11. 7 88 103 4, 400 550 12 O. 70Pulp II 13 0 2.4 17 .1 0 68 0.36 25 43 9.8 75 127 3, 200 16 44 0.64 4565 11. 4 90 111 3, 700 420 0. 70 Pnlps separated from pulp II:

Pulp IV 13 0 2. 3 0 89 0.38 49 9. 9 80 124 3, 700 36 0. 67 45 7O 11. 790 105 4, 200 550 13 O. 72 Pulp VI 12 0 1. 7 10 0 73 0.32 25 44 9. 0 65136 2, 300 8 49 0. 62 45 65 10. 7 82 116 3, 300 290 15 0. 65 Pulp I+II13.5 0 3. 4 21 1. 1 80 0.41 25 48 10.0 84 118 4,000 26 36 0. 67 45 7311. 7 94 103 4, 400 890 14 0.72 Pulp V+IV 12 0 2. 3 17 0 86 0. 36 25 499. 8 79 123 3, 909 22 37 O. 66 45 72 11.7 91 107 4,400 550 15 0. 71

TABLE 4.DATA OF ANALYSIS OF THE ORIGINAL PULP AND OF THE SEPARATEDPULPS, RESPECTIVELY (UNBLEACHED BIRCH SULPHATE PULP) Valley beatingDenomination Degree of Time of Breaking Burst Tear Folding Porosity,Absorption, Volume beating, SR beoting,min. length, km. factor factornumber sec./100 cu. nun. weight, gJeu.

cm. cm.

Original pulp 14. 5 0 4. 8 25 1 86 0. 59 25 14 8. 8 57 75 900 27 34 0.71

Pulp I 15.0 0 5. 4 30 3 67 0.61 25 14 9. 2 60 75 800 32 35 0. 74

Pulp II 13.0 0 3. 4 16 106 0.50 25 20 9.2 60 74 950 29 0. 62

TABLE 5.DATA OF ANALYSIS OF THE ORIGINAL PULP AND OF THE SEPARAT EDPULPS, RESPECTIVELY (UNBLEACHED PRUCE SULPHITE PULP) Valley beatingDenomination Degree of Time of Breaking Burst Tear Folding Porosity,Absorption, Volume beating, SR beating, min. length, km. factor factornumber see/100 cu. mm. weight, gJcu.

em. C111.

Original pulp 13. 5 0 6. 5 42 7 58 0. 66 25 1O 9. 1 57 200 14 0. 77 4521 9. 8 59 1, 200 0 O. 84 Pulp I 14. 5 0 6. 8 46 12 50 0. 67 25 8 9. 662 500 12 0. 75 45 17 10. 0 67 1, 200 1 O. 81 Pulp II 12. 0 0 4. 6 31 1.S6 0. 62 25 12 8. 3 54 200 23 O. 73 45 24 9. 2 1, 200 0 0. 80

References Cited Having now described my invention What I claim asUNITED STATES PATENTS new and desire to secure b Letter Patent 's:

Th h V fib d t 2,377,524 6/1945 Samson 209 211 3 P c ss V C C mPI'ISeSeI'lZlng WOO 1n 0 Hesch FOREIGN PATENTS 76,122 10/1954 Netherlands.

DONALL H. SYLVESTER, Primary Examiner.

MORRIS O. WOLK, H. L. MARTIN, R. A. OLEARY,

Examiners.

75 H. CAINE, F. W. LU'ITER, Assistant Examiners.

